Downhole Tubular Section Mill

ABSTRACT

A casing section mill has a main body with cut-outs to accommodate casing section mill blades mounted thereon, and stabilizer inserts mounted in the cut-outs below the blades. The stabilizer inserts yield an outer diameter substantially the same as the drift inner diameter of the casing being milled, thereby providing positive centralization and stabilization of the blades. The casing section mill may be rotated by a downhole positioned positive displacement motor in the drillstring, by drillstring rotation from the surface, or a combination of downhole positive displacement motor and drillstring rotation.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application claims priority to U.S.provisional patent application Ser. No. 62/632,509, filed Feb. 20, 2018,for all purposes. The disclosure of that provisional patent applicationis incorporated herein, to the extent not inconsistent with thisdisclosure.

BACKGROUND Field of the Invention

This invention relates to apparatus for downhole cutting of tubulars ina wellbore.

Various apparatus have been developed for cutting of tubulars, downholein a wellbore. The Applicant herein holds various patents and patentapplications directed to such apparatus.

SUMMARY OF THE INVENTION

The apparatus comprises a main body designed to accommodate the linkagearms and cutter bases of Applicant's Well Bore Casing Mill, as disclosedin Applicant's U.S. Pat. No. 9,695,660, along with the internal pistonoperating system; however, the linkage arms and cutter bases of thatapparatus may be replaced with more conventional section mill (“CSM”)blades. As disclosed in that patent, the main body has a pair oflongitudinal cut-outs on either side, in which the linkage arms andcutter bases operate.

In the tubular section mill embodying the principles of the presentinvention, the CSM blades are rotatably mounted in the cut-outs in themain body, generally in an upper part of the main body, and rotatablefrom a first, substantially retracted position, to a second,substantially extended position, by the internal operating piston inresponse to fluid flow. Notably, a number of different types of CSMblades, configured to cut windows in the tubulars, mill sections of thetubulars, etc. may be installed as desired. Depending upon the bladeconfiguration, cutting in either or both of a downhole and upholedirection may be done.

In the lower part of the main body, in the cut-outs in which linkagearms and cutter bases would retract (in the apparatus disclosed in U.S.Pat. No. 9,695,660), are mounted non-expanding stabilizer inserts. Theoverall tool diameter yielded by the stabilizer inserts is sized tosubstantially match the drift diameter of the tubular string, namely thecasing string, internal diameter (ID) within which the tool is beingrun; that is, closely matched to the drift diameter of the tubular inwhich the stabilizer insert is positioned and (usually) that is beingmilled.

Downhole rotation of the apparatus can be had by surface rotation of theentire drillstring, or in some instances preferably by a downholedevice, namely a positive displacement motor (“PDM”). A combination ofsurface rotation and downhole rotation via PDM can be used. In somesettings a downhole turbine could be used.

An exemplary bottom hole assembly (“BHA”) incorporating the presentapparatus would include (starting at the downhole end of the BHA) a CSMdressed with blades to suit the particular job (e.g. casing cutting,milling, etc.) and with stabilizer inserts yielding an outer diameterclosely matching the drift ID of the casing being milled; a jetted topsub; a float sub with a ported float; a PDM; and drill collars asappropriate, connecting to the work string on which the BHA is loweredinto the wellbore.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematical view of the apparatus embodying the principlesof the present invention, along with other elements of a typical bottomhole assembly.

FIG. 2 is a perspective view of the main body of the apparatus embodyingthe principles of the present invention, showing more detail of thestabilizer inserts mounted in the main body, namely in the lower sectionof the cut-outs.

FIG. 3 is another perspective view of the apparatus, showing the CSMblades mounted in the main body and in an outwardly extended position,in addition to the stabilizer inserts.

FIGS. 4a-4c are various side views of the apparatus, with the blades ina retracted position. FIGS. 4a and 4c are views rotated 90 degrees fromone another. FIG. 4b is a side view in partial cross section of theapparatus, along section line A-A in FIG. 4c , showing the blades in aretracted position and elements of the internal operating mechanism,namely the piston. Note that the stabilizer inserts are not mounted inthe main body in these views.

FIGS. 5a-5c are various side views of the apparatus, with the blades inan extended position. FIGS. 5a and 5c are views rotated 90 degrees fromone another. FIG. 5b is a side view in partial cross section of theapparatus, along section line A-A in FIG. 5c , showing the blades in anextended position and elements of the internal operating mechanism,namely the piston. Note that the stabilizer inserts are not mounted inthe main body in these views.

FIG. 6 is a view of an exemplary placement of the casing section mill ofthe present invention in a downhole position in a casing string, showingthe tool engaged with the casing and cutting and/or milling a windowtherein.

DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT(S)

While various downhole tubular section mills can embody the principlesof the present invention, with reference to the drawings some of thepresently preferred embodiments can be described.

FIG. 1 is a schematical view of a typical bottom hole assembly (“BHA”)comprising the casing section mill embodying the principles of thepresent invention. While various assemblies may be employed, dependingupon the particular job, by way of example (starting at the downholeend) the BHA comprises a casing section mill (“CSM”) 10 dressed withblades 40 to suit the particular job, and with stabilizer inserts 30 tomatch tubular inner diameters; a jetted top sub (noted); a float sub,preferably with a ported float (noted); a positive displacement motor orPDM 100; and drill collars as appropriate, connecting to the workstring. It is understood that different BHA components may be useddepending on the job. Notably, in this exemplary embodiment, PDM 100 isused to generate downhole rotation of the apparatus. It is understoodthat surface rotation of the entire drillstring, in combination withdownhole rotation via PDM 100 (or turbine), is encompassed within theinvention.

It is understood that the CSM embodying the principles of the presentinvention generally comprises the main body and piston operating systemdisclosed in Applicant's U.S. Pat. No. 9,695,660, and the disclosure ofthat patent is incorporated herein by reference, to the extent needed toset out the general structure of the instant apparatus.

FIG. 2 is a more detailed perspective view of CSM 10, showing main body20 of the apparatus without blades 40 installed. Note theuphole/downhole directions indicated. FIG. 2 shows stabilizer inserts 30mounted in the lower section of the cut-outs 22 within main body 20.Main body 20 has a longitudinal bore 24 in at least an upper sectionthereof, through which fluid is pumped. Preferably, stabilizer inserts30 are sized to yield an outer diameter of CSM 10 nearly equal or equalto the drift diameter of the tubular within which stabilizer inserts 30are rotating, so as to minimize eccentric movement of the entireapparatus within the tubular. In addition, stabilizer inserts 30 arepreferably positioned immediately below (or as close as reasonablypossible) the blade location, again to assist in centralization of theoverall tool. Typically, stabilizer inserts 30 are positioned in androtating in a casing string which is being cut or milled by blades 40positioned just uphole from stabilizer inserts 30. The diameterresulting from the stabilizer inserts 30 and the close positioning (in adownhole position) result in a very stable cutting path of blades 40,and very much increased efficiency of cutting.

FIG. 3 is another perspective view, showing main body 20 with stabilizerinserts 30 installed, and additionally with blades 40 installed. In FIG.3, blades 40 are in a second, open position.

FIGS. 4a-4c are side views of casing section mill 10. FIGS. 4a and 4care exterior views rotated 90 degrees apart. FIG. 4b is a section viewalong section line A-A of FIG. 4c . These three views show apparatuswith blades 40 installed and showing some detail of operating mechanism42. In particular, as disclosed in U.S. Pat. No. 9,695,660, operatingmechanism 42 comprises a slidable piston 44, which moves in a downholedirection in response to fluid flow in that direction; piston 44 has abore 43 and preferably a removable jet therein. In these figures, blades40 are in a first, retracted position.

FIGS. 5a-5c are further side views of casing section mill 10, generallycorresponding to the views in FIGS. 4a-4c . FIGS. 5a and 5c are exteriorviews rotated 90 degrees apart. FIG. 5b is a section view along sectionline A-A of FIG. 5c . Similar to FIGS. 4a-4c , these three views showapparatus with blades 40 installed and showing some detail of operatingmechanism 42. In these FIGS. 5a-5c , blades 40 are in a second, open orextended position. A lower end of piston 44 bears on heel portions 41 ofblades 40, rotating them into their second, open or extended position.

Fabrication and Materials

Casing section mill 10 is preferably formed from high strength metalsand with fabrication techniques generally known in the relevant art(welding, machining, forging, etc.). Non-metal components are used asappropriate for seals, etc.

Methods of Use of the Apparatus and System

The present apparatus may be considered as part of a system, theapparatus and its methods of use embodying the present invention. Thescope of the present invention encompasses not only casing section mill10 alone, but also a system comprising casing section mill 10, alongwith various methods of use. As noted above, casing section mill or CSM10 is beneficially part of a downhole tubular milling system employingPDM 100. FIG. 6 is a view of an exemplary setting of use of casingsection mill 100. Casing section mill 100 is positioned at a desiredlocation in the casing 200. As can be seen, the outer diameter ofstabilizer inserts 30 closely match the inner diameter, preferably thedrift diameter, of casing 200. Blades 40 are extended outwardly to anoperating or cutting position, by fluid flow through the drillstring andbore 24 of casing section mill 10 acting on piston 44. As can be seen inFIG. 6, a section of casing has already been cut/milled out, and blades40 are bearing on the uppermost cut end. Rotation of casing section mill10, combined with weight imposed on the cutting surface by the bottomhole assembly, results in continued cutting. Use of a PDM to achievedownhole rotation of casing section mill 10 permits achieving a higherrotation speed of casing section mill 10, for example 100-200 RPM.Alternatively, a downhole rotation speed of casing section mill 10 of(for example) 60 RPM may be achieved via PDM 100, in addition to surfacerotation of the entire drillstring (for example) 60 RPM, resulting in afinal rotation speed of casing section mill 10 of 120 RPM. By achievingpart of the overall rotation speed of casing section mill 10 via surfacerotation, torque readings may be easily taken at the surface.

It is understood that methods of both cutting and milling tubulars usinga system comprising casing section mill 10 are encompassed within thepresent invention. The method may include the steps of: lowering abottom hole assembly comprising casing section mill 10 and a PDM to adesired depth in a wellbore, on a drillstring; commencing fluid flowthrough the drillstring, the PDM, and casing section mill 10, therebymoving blades 40 outwardly into contact with the casing wall or apreviously cut surface, in order to continue milling, and resulting inrotation of casing section mill 10; alternatively, if desired,commencing rotation of the drillstring from the surface; monitoringstring weight, weight on the tool downhole, and torque at the surface,in order to monitor and optimize the milling function.

Various types of blades 40 may be used, depending on the particulartubular cutting/milling function being performed. By way of example:

-   -   blades can be used which comprise multiple hardened inserts, for        both cutting an initial window in a casing string, and for        milling a section of the casing string    -   traditional casing section mill blades can then be substituted        if desired for milling longer sections    -   if desired, both blades 40 and stabilizer inserts 30 may be        removed from a given main body 20, and that same main body 20        may be “dressed” or equipped with linkage arms, cutter bases and        cutters, as disclosed in Applicant's U.S. Pat. No. 9,695,660;        this versatility is a significant benefit of the system    -   blades 40 can be configured to enable cutting/milling in both a        downhole and an uphole direction, with uphole milling enabled        with sufficient downward force applied to piston 44.

CONCLUSION

While the preceding description contains many specificities, it is to beunderstood that same are presented only to describe some of thepresently preferred embodiments of the invention, and not by way oflimitation. Changes can be made to various aspects of the invention,without departing from the scope thereof. For example, dimensions can bevaried to suit particular applications; the types and configurations ofblades can be varied depending upon the types and dimensions of tubularsbeing cut, and the length of the cuts; any combination of surface anddownhole rotation (which may be by PDM or turbine) may be used;sequences of dressing the apparatus with different blades, with/withoutstabilizer inserts may be used to achieve different jobs.

Therefore, the scope of the invention is to be determined not by theillustrative examples set forth above, but by the appended claims andtheir legal equivalents.

We claim:
 1. A casing section mill, comprising: an elongated main bodyhaving upper and lower ends and a central bore through an uphole sectionthereof, with a means for connecting said upper end to a drillstring,said main body further comprising a pair of elongated cutouts extendingto a position proximal said lower end; a piston slidably disposed insaid central bore, said piston movable in response to fluid flow throughsaid central bore of said main body; a pair of blades rotatably disposedin said main body, said blades comprising heel sections, wherein saidpiston bears on said heel sections in response to fluid passage throughsaid bore of said main body, moving said blades from a first, retractedposition to a second, extended position to engage a casing string forcutting or milling; a plurality of stabilizer inserts removably mountedin a lower or downhole portion of said elongated cutouts, in a downholedirection from said blades, said stabilizer inserts sized to yield anouter diameter across said mounted stabilizer inserts substantiallyequal to the inner drift diameter of the casing string being cut ormilled.
 2. The casing section mill of claim 1, wherein said bladescomprise elongated cutters having multiple hardened inserts therein. 3.The casing section mill of claim 2, wherein said stabilizer insertscomprise elongated inserts with an upper end positioned proximal saidblades when said blades are in their first, retracted position, and alower end extending substantially to a lower or downhole end of samemain body, and wherein said lower end of said stabilizer insertscomprise tapered profiles to aid in movement downhole in a wellbore. 4.An assembly for milling casing in a wellbore, comprising: a drillstringcomprising a bottomhole assembly, said bottomhole assembly comprising: acasing section mill, said casing section mill comprising: an elongatedmain body having upper and lower ends and a central bore therethrough,said main body further comprising a plurality of elongated cutoutsextending to a position proximal said lower end; a piston slidablydisposed in said central bore, said piston movable in response to fluidflow through said central bore of said main body; a pair of bladesrotatably disposed in said main body, said blades comprising heelsections, wherein said piston bears on said heel sections in response tofluid passage through said bore of said main body, moving said bladesfrom a first, retracted position to a second, extended position toengage a casing string for cutting or milling; a plurality of stabilizerinserts removably mounted in a lower or downhole portion of saidelongated cutouts, in a downhole direction from said blades, saidstabilizer inserts sized to yield an outer diameter across said mountedstabilizer inserts substantially equal to the inner drift diameter ofthe casing string being cut or milled; and a positive displacement motordisposed in an uphole position from said casing section mill, wherebyrotation of said positive displacement motor due to fluid flow resultsin rotation of said casing section mill.
 5. The casing section mill ofclaim 4, wherein said stabilizer inserts comprise elongated inserts withan upper end positioned proximal said blades when said blades are intheir first, retracted position, and a lower end extending substantiallyto a lower or downhole end of same main body, and wherein said lower endof said stabilizer inserts comprise tapered profiles to aid in movementdownhole in a wellbore.
 6. A method of milling casing, comprising thesteps of: a) providing a casing section mill, comprising: an elongatedmain body having upper and lower ends and a central bore through anuphole section thereof, with a means for connecting said upper end to adrillstring, said main body further comprising a pair of elongatedcutouts extending to a position proximal said lower end; a pistonslidably disposed in said central bore, said piston movable in responseto fluid flow through said central bore of said main body; a pair ofblades rotatably disposed in said main body, said blades comprising heelsections, wherein said piston bears on said heel sections in response tofluid passage through said bore of said main body, moving said bladesfrom a first, retracted position to a second, extended position toengage a casing string for cutting or milling; a plurality of stabilizerinserts removably mounted in a lower or downhole portion of saidelongated cutouts, in a downhole direction from said blades, saidstabilizer inserts sized to yield an outer diameter across said mountedstabilizer inserts substantially equal to the inner drift diameter ofthe casing string being cut or milled; b) running said casing sectionmill downhole into a wellbore, on a drillstring; c) positioning saidcasing section mill within a section of casing to be milled; and d)commencing fluid flow through said drillstring, said positivedisplacement motor and said casing section mill, thereby extending saidblades and engaging said blades with said casing string and rotatingsaid casing section mill.
 7. The method of claim 6, comprising thefurther step of: e) rotating said drillstring from the surface,resulting in a rotational speed of said casing section mill from thecombination of said positive displacement motor and said drillstringrotation.
 8. The method of claim 7, comprising the further step of: f)monitoring torque readings on said drillstring.